Recently, there was a swarm of threads of complaints in that various AdSense forums about how it appears the Google AdSense earnings reports are not adding up correctly. I’ll isolate two Google AdSense Help Threads that have discussion about this.

The issue is really not a calculation error but rather that you are looking at the wrong date ranges.

Alan7769 explained in the thread that the problem is, “since last payment reporting is going back exactly 30 days from the current day, instead of back to the first of the month after your last payment was done.” Alan recommends you use the “advanced reports and put in the actual dates from and to for your report, at least until adsense fixes the problem with the since last payment reporting.”

There is a terrible amount of confusion now about this so hopefully Google will make things a bit clearly on those default reports.

Forum discussion at Google AdSense Help Threads.

Update: Google has posted a statement:

Still, not all publishers are convinced or happy.